Process for controlling static properties of synthetic textile fibers



United States Patent @fifice 3,053,128 Patented Nov. 13., 1962 3,063,128 PROCESS FOR CQNTROLHNGSTATIC PROPER- TlES F SYNTHETNI TEXTELE FIBERS Gibson 8. Etchison, Shawrnut, Ala, assignor to West Point Manufacturing Company, West Point, Ga, a corporation of Georgia No Drawing. Filed Apr. 9, 1959, Ser. No. 805,127

12 Claims. (Cl. 2$-'75) This invention relates to textile fibers, and in particular to the processing of synthetic textile fibers in conventional operations preceding and including formation into fabric, either woven or non-woven. In processing synthetic fibers by operations such as picking, carding, drafting, spinning and weaving, many types of fibers exhibit a strong tendency to build up and retain high static charges, usually positive, whieh cause the fibers to repel each other and balloon out, frequently making it difficult or impossible to satisfactorily control and process the fibers.

In many cases, this condition may be alleviated by increasing the moisture content of the fibers, and this expedient has been utilized to improve the processing of such fibers by maintaining a highly humid atmosphere in the work spaces. Maintaining an atmosphere of high humidity, however, is expensive and uncomfortable for operating personnel, tends to rust machinery and is otherwise disadvantageous. High humidity, moreover, does not always eifect satisfactory processing. Several types of reclaimed waste nylon cut staple fibers, for example, are impossible to card or otherwise process satisfactorily, even though maintained in a warm atmosphere of substantially 100% relative humidity, without resort to extensive blending.

A principal object of the present invention is to provide a simple and inexpensive procedure for positively controlling the static properties of synthetic textile fibers, of cut staple or continuous filament type, whereby the fibers may be subjected to conventional textile processing operations with elficiency, and without difiiculty due to static. The process permits operation under comfortable, low humidity atmospheric conditions.

A further object of the invention is to permit the use in textile operations of inexpensive fibers hitherto incapable of such use. A particular object of the invention is to prevent the build up on textile fibers of static electric charges of positive character, by depositing thereon montmorillonite particles of colloidal size, optionally with the addition of a minor proportion of humectant material. Further objects will be in part obvious and in part pointed out hereinafter.

The invention is of particular merit in connection with the use of synthetic fibers high in triboelectric series (see S. P. Hersh and D. I. Montgomery, Static Electrification of Filaments, Textile Research Journal, vol. 25, April 1955, page 279), which fibers are prone to develop and retain a high positive static charge when frictioned. The invention is most useful with fibers of the class described Which exhibit a moisture regain of less than 5%, including particularly fibers composed of polyamide material (nylon), cellulose triacetate (Arnel), polyesters (Dacron), and acrylic and related materials (Grlon, Acrilan, Dynel). The moisture regain referred to represents the normal percentage by weight of moisture in the fiber based on the dry Weight of the fiber. If the fibers are dried to a bone dry condition, they will subsequently pick up moisture from the atmosphere substantially to the normal moisture regain point, and if the fibers are wetted, they will dry out in the atmosphere substantially to the same point.

In accordance with the present invention, the fibers prior to processing, for example in the opening room, are treated with an aqueous dispersion or suspension of montmorillonite. Montmorillonite is a hydrous substituted aluminum silicate, with a micaceous structure and an exceptionally small ultimate particle size, less than 0.5 micron in maximum dimension. Montmorillonite is noted for its ability to swell in Water, and disperses readily in cold water into particles of colloidal size. Varying proportions of calcium, magnesium andsodiurn ions are found in the cation exchange positions, depending on the source of the material. Sodium montmorillonite is preferred in the present invention.

After application of the suspension the fibers may be dried, as in air or a current of warm air, or even in the course of processing, whereby montmorillonite particles of colloidal size are deposited on the fibers and adhere tenaciously thereto. Under special conditions, such as relatively high humidity, 0.5% by weight of montmorillonite particles, based on the dry weight of the fibers, is sufiicient to minimize or eliminate the tendency of the fibers to build up and retain a static electric charge, and to insure processing of the fiber without difiiculty due to static. One percent by weight of montmorillonite particles appears to preclude the build up of static charges on the fibers under all ordinary conditions. The application of somewhat more than 1% of montmorillonite particles, for example 1%% or 1 /z%, to some fibers appears to give rise to a tendency to build up a negative potential of minor proportions, but larger percentages, of the order of 4 or 5% montmorillonite particles, avoid this tendency altogether, and the fibers so treated exhibit no measurable static charge under any frictioning conditions. That is, the fibers may be picked, carded, drafted, spun and/ or Woven in conventional manner, with complete freedom from static charge and difficulties resulting therefrom. More than 5% of montmorillonite particles may be employed, but no additional benefit appears to flow therefrom.

The montmorillonite suspension may be applied in any conventional manner, as by spraying, or by means of a bath or applicator roll. Spraying is preferred as simplest and least expensive. While in spraying suspension onto the fibers perfect distribution is not attained, the particle distribution on the fibers is yet effective to preclude any difiiculty in processing due to static charge.

In spraying, it is desirable to apply at least 5% by weight of montmorillonite, based on the dry weight of the fibers. For spraying, asuspension of 10% by Weight of sodium montmorillonite in water may be employed, or a suspension of 30% by Weight of calcium montmorillonite in water. 1

Application of the suspension in a bath is more expensive, due primarily to the fact that more extensive drying is necessitated, but permits the use of less montmorillonite with complete effectiveness. Bath application may be readily regulated to effect wet pickup on the fibers, so that the desired weight of particles on the fibers may be attained by use of a suspension of the desired percentage of montmorillonite in the bath. Bath application is well adapted, also, for the treatment of continuous filament fibers, as in a slasher. Application by means of an applicator roll is particularly advantageous in the treatment of continuous filament nylon fibers, and as will be recognized, the montmorillonite may be applied to the filaments as a finish shortly after extrusion of the filaments.

In many cases, the action of the montmorillonite particles in preventing build up of static charge appears to be enhanced by the addition of a hurnectant material. A preferred humectant material is potassium acetate, which may be dissolved in the montmorillonite suspension, the potassium acetate being used preferably in amount equal to at least 10% by Weight of the weight of the montmorillonite in the suspension.

Other humectant materials which may be employed are calcium chloride, sodium sulfate, glycerin and sorbitol. Obviously, dyes and other materials may be included in the suspension, if desired.

While the function and operation of the montmorillonite particles on the textiie fibers is not fully understood, it is known that the montmorillonite disperses in water into ultimate particles of plate-like shape, having largest dimension less than 0.5 micron. Montinorillonite is a solid crystallite of colloidal size, which adheres tenaciously to the fibers when dry, possibly by means of electrical forces. It is thought that the montmorillonite particles may generate or attract static charges of negative sign, which counterbalance static charges of opposite sign. It may also be that the montmorillonite particles attract and hold moisture on the fiber surface, thereby serving in the manner of a semi-conductor to quickly dissipate accumulations of static charge which may appear. Some credence is given to this theory by the circumstance that the addition of a humectant material to the particles in some cases definitely improves their anti-static function.

The invention is further illustrated but not limited by the following examples.

- Example I A bale of nylon 66 cut staple fiber, 3 denier and 1 /2" staple length, is opened and uniformly sprayed with a 10% by weight suspension of sodium montmorillonite in water, the rate of spray application being such as to deposit about 5% (dry) of montmorillonite on the fibers, based on the dry weight of the fibers. The sprayed fiber is dried by a current of warm air. The dispersed montmorillonite particles adhere tenaciously to the fibers, which are then picked, carded, drafted, spun and woven in conventional manner. Substantially all of the montmorillonite is retained on the fibers through the processing operations, which are carried out without any evidence of static charge on the fibers or any difiiculty due to static.

Example II The procedure of Example I is repeated, with the exception that the opened fiber is sprayed with a 30% by weight suspension of calcium montmorillonite in water, to deposit 5% on the fibers. The anti-static properties of the treated fibers appear to be essentially as good as in the case of sodium montmorillonite.

Example Ill Reclaimed waste nylon staple fiber is opened and uniformly sprayed with a suspension containing, by weight, 89 parts water, parts sodium montmorillonite and 1 part potassium acetate, the rate of spray application being such as to deposit about 5% (dry) of montmorillonite on the fibers, based on the dry weight of the fibers. The sprayed fiber is tumbled and air dried, whereupon the fibers are picked, carded, drafted and spun in conventional manner. The textile processing operations are carried out without ditficulty due to static.

Example IV The procedure of Example III is repeated, with the exception that the opened fiber is sprayed with a suspension containing, by weight, 70 parts water, parts calcium montmorillonite and 6 parts potassium acetate. The fibers exhibit the same anti-static properties as in the case of Example HI.

Example V Nylon 6 staple fibers are opened and immersed in a bath containing, by weight, 99% water and 1% sodium montmorillonite. The fiber is removed from the bath and squeezed to effect 100% wet pickup, based on the dry fiber weight. The treated fiber is then dried in a current of warm air. The treated and dried fiber is then carded, and the carding operation is carried out with outstanding efiiciency, the fiber exhibiting no evidence whatsoever of static charge.

xample Vl Nylon 66 staple fibers are opened and immersed in a bath containing, by weight, 94.5% water, 5.0% sodium montmorillonite, and 0.5% potassium acetate. The fiber is removed from the bath and squeezed to effect wet pickup, based on the dry fiber weight. The treated fiber is then dried in a current of warm air, carded and drafted. The carding and drafting operations are readily and efiiciently carried out, the treated fiber exhibiting no evidence of static charge.

It will thus be seen that there has been provided by this invention a method in which the various objects hereinbefore set forth, together with many practical advantages, are successfully achieved. As various possible embodiments may be made of the novel features of the above invention, all without departing from the scope thereof, it is to be understood that all matter hereinbefore set forth is to be interpreted as illustrative, and not in a limiting sense.

What is claimed is:

1. Process for controlling the static properties of synthetic textile fibers high in the triboelectric series and exhibiting moisture regain not exceeding 5.0% comprising the steps of applying an aqueous suspension of montmorillonite to the fibers, drying the fibers to deposit thereon at least about 0.5% by weight of montmorillonite particles, and then subjecting the fibers to a textile processing operation.

2. Process as defined in claim 1, wherein said textile fibers are nylon.

3. Process as defined in claim 1, wherein about 5.0% by weight of montmorillonite particles is deposited on the fibers.

4. Process as defined in claim 1, wherein said suspension is applied in the form of a spray.

5. Process as defined in claim 1, wherein the subsequent textile processing operation is carding.

6. Process for controlling the static properties of synthetic textile fibers prone to develop and retain a positive static charge when frictioned, comprising the steps of applying to the fibers an aqueous suspension of montmorillonite containing a minor proportion of a humectant material, and drying the fibers to deposit thereon at least about 1.0% by weight of montmorillonite particles.

7. Process as defined in claim 6, wherein said humectant material is potassium acetate.

8. Process as defined in claim 7, wherein said potassium acetate is present in amount equal to at least 10% by weight of said montmorillonite.

9. Process for controlling the static properties of synthetic textile staple fibers high in the triboelectric series and exhibiting moisture regain not exceeding 5.0%,

comprising the steps of applying an aqueous suspension of montmorillonite to the fibers, drying the fibers to deposit thereon at least about 0.5% by weight of montmorillonite particles, and then subjecting the fibers to a textile fiber processing operation of the nature of picking, carding and drafting.

10. Process as defined in claim 9, wherein said aqueous suspension contains a minor proportion of a humectant material.

11. Process as defined in claim 9, wherein said aqueous suspension contains a minor proportion of potassium acetate.

12. Process as defined in claim 9, wherein said staple fibers are nylon.

(Qther references on foiiowing page) 5 Dreyfus July 13, ,1937 Cadwell et a1. Nov. 17, 1942 Conaway Feb. 26, '1946 Feild et a1. Apr. 6, 1948 Moody Feb. 26, 1952 5 Moody Feb. 26, 1952 Cogovan et a1 Dec. 23, 1952 Powers Apr. 14, 1953 Cohen et a1. Apr. 27, 1954 Nickerson Feb. 1, 1955 10 Repp July '10, 1956 Cogovan et a1. Oct. 29, 1957 6 Healy May 5, 1959 OTHER REFERENCES Bentonite, by Silica Products Company, 700 Baltimore Avenue, Kansas City, Mo., 1934 (pages 5 and 36 of interest only).

Processing Du Pont Nylon Staple on the Woolen System, Du Pont Technical Information Bulletin N31, November 1955.

Processing Du Pont Nylon Staple on the Worsted System, Du Pont Technical Information Bulletin N-32, November 1955. 

1. PROCESS FOR CONTROLLING A STATIC PROPERTIES OF SYNTHETIC TEXTILE FIBERS HIGH IN THE TRIBOELECTRIC SERIES AND EXHIBITING MOISTURE REGAIN NOT EXCEEDING 5.0% COMPRISING THE STEPS OF APPLYING AN AQUEOUS SUSPENSION OF MONTMORILLONITE TO THE FIBERS, DRYING THE FIBERS TO DEPOSIT THEREON AT LEAST ABOUT 0.5% BY WEIGHT OF MONTMORILLONITE PARTICLES, AND THEN SUBJECTING THE FIBERS TO A TEXTILE PROCESSING OPERATION. 